CN111010124B - Bulk acoustic wave resonator having electrode with void layer, filter, and electronic device - Google Patents
Bulk acoustic wave resonator having electrode with void layer, filter, and electronic device Download PDFInfo
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Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/02007—Details of bulk acoustic wave devices
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
- H03H9/17—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator
- H03H9/171—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator implemented with thin-film techniques, i.e. of the film bulk acoustic resonator [FBAR] type
- H03H9/172—Means for mounting on a substrate, i.e. means constituting the material interface confining the waves to a volume
- H03H9/173—Air-gaps
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/46—Filters
- H03H9/54—Filters comprising resonators of piezo-electric or electrostrictive material
Abstract
The invention relates to a bulk acoustic wave resonator comprising: a substrate; an acoustic mirror; a bottom electrode; a top electrode; and a piezoelectric layer disposed between the bottom electrode and the top electrode, wherein: the bottom electrode and/or the top electrode are gap electrodes, each gap electrode comprises a gap layer, a first electrode and a second electrode, the gap layer is formed between the first electrode and the second electrode in the thickness direction of the resonator, and the first electrode is in surface contact with the piezoelectric layer; and the gap electrode includes a first surface on the first electrode side, a second surface on the second electrode side, the first surface and the second surface being opposed to each other in a thickness direction of the resonator, and the gap layer being located between the first surface and the second surface; the resonator further includes a plurality of protrusions extending from the first surface and/or the second surface into the void layer in a thickness direction of the resonator, the protrusions extending to a height less than a thickness of the void layer. The invention also relates to a filter with the resonator and an electronic device with the filter or the resonator.
Description
Technical Field
Embodiments of the present invention relate to the field of semiconductors, and in particular, to a bulk acoustic wave resonator, a filter having the resonator, and an electronic device having the resonator or the filter.
Background
Electronic devices have been widely used as basic elements of electronic equipment, and their application range includes mobile phones, automobiles, home electric appliances, and the like. In addition, technologies such as artificial intelligence, internet of things, 5G communication and the like which will change the world in the future still need to rely on electronic devices as a foundation.
Electronic devices can exert different characteristics and advantages according to different working principles, and among all electronic devices, devices working by utilizing the piezoelectric effect (or inverse piezoelectric effect) are an important class, and the piezoelectric devices have very wide application scenarios. Film Bulk Acoustic Resonator (FBAR, also called Bulk Acoustic Resonator, BAW for short) is playing an important role in the communication field as an important member of piezoelectric devices, especially FBAR filters have increasingly large market share in the field of radio frequency filters, FBARs have excellent characteristics of small size, high resonance frequency, high quality factor, large power capacity, good roll-off effect and the like, the filters gradually replace traditional Surface Acoustic Wave (SAW) filters and ceramic filters, play a great role in the radio frequency field of wireless communication, and the advantage of high sensitivity can also be applied to the sensing fields of biology, physics, medicine and the like.
The structural main body of the film bulk acoustic resonator is a sandwich structure consisting of an electrode, a piezoelectric film and an electrode, namely a layer of piezoelectric material is sandwiched between two metal electrode layers. By inputting a sinusoidal signal between the two electrodes, the FBAR converts the input electrical signal into mechanical resonance using the inverse piezoelectric effect, and converts the mechanical resonance into an electrical signal for output using the piezoelectric effect.
The rapid development of communication technologies requires that the operating frequency of the filter is continuously increased, for example, the frequency of a 5G communication band (sub-6G) is 3GHz-6GHz, and the frequency is higher than that of 4G. For bulk acoustic wave resonators and filters, high operating frequencies mean that the film thickness, especially of the electrodes, is further reduced; however, the main adverse effect of the reduction of the thickness of the electrode film is the reduction of the Q value of the resonator caused by the increase of the electrical loss, especially the reduction of the Q value at the series resonance point and the vicinity of the frequency thereof; accordingly, the performance of the high operating frequency bulk acoustic wave filter also deteriorates significantly as the Q value of the bulk acoustic wave resonator decreases.
A solution to improve bulk acoustic wave performance by providing a void layer in the electrode has been proposed.
Disclosure of Invention
The invention is provided in order to further improve the performance of the bulk acoustic wave resonator with the electrode containing the gap layer or ensure that the performance of the bulk acoustic wave resonator has good stability in working.
According to an aspect of an embodiment of the present invention, there is provided a bulk acoustic wave resonator including:
a substrate;
an acoustic mirror;
a bottom electrode;
a top electrode; and
a piezoelectric layer disposed between the bottom electrode and the top electrode,
wherein:
the bottom electrode and/or the top electrode are gap electrodes, each gap electrode comprises a gap layer, a first electrode and a second electrode, the gap layers are formed between the first electrodes and the second electrodes in the thickness direction of the resonator, and the first electrodes are in surface contact with the piezoelectric layers; and is
The gap electrode includes a first surface on the first electrode side, a second surface on the second electrode side, the first surface and the second surface being opposite to each other in a thickness direction of the resonator, and a gap layer located between the first surface and the second surface;
the resonator further includes a plurality of protrusions extending from the first surface and/or the second surface into the void layer in a thickness direction of the resonator, the protrusions extending to a height less than a thickness of the void layer.
Embodiments of the present invention also relate to a filter comprising the bulk acoustic wave resonator described above.
Embodiments of the invention also relate to an electronic device comprising a filter as described above or a resonator as described above.
Drawings
These and other features and advantages of the various embodiments of the disclosed invention will be better understood from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate like parts throughout, and in which:
fig. 1 is a schematic partial cross-sectional view of a gap electrode of a bulk acoustic wave resonator according to an exemplary embodiment of the present invention, a second top electrode of the gap electrode being provided with a protrusion;
FIG. 2 is a schematic view of the gap electrodes of FIG. 1 attached to each other;
FIG. 3 is a partial enlarged view of the area in FIG. 2;
fig. 4 is a schematic partial cross-sectional view of a gap electrode of a bulk acoustic wave resonator according to an exemplary embodiment of the present invention, a first top electrode of the gap electrode being provided with a protrusion;
fig. 5 is a schematic partial cross-sectional view of a bulk acoustic wave resonator according to another exemplary embodiment of the present invention, the first top electrode being provided with a passivation layer, a surface of the passivation layer being provided with a protrusion;
fig. 6A is an exemplary schematic diagram of a protrusion arrangement according to an exemplary embodiment of the present invention, wherein the protrusion is arranged on the second top electrode side;
FIG. 6B is a schematic top view of FIG. 6A;
FIG. 7 is a schematic view of a protrusion distribution according to an exemplary embodiment of the present invention;
FIG. 8 is a schematic view of the profile of a protrusion according to an exemplary embodiment of the present invention;
FIGS. 9A and 9B are perspective and cross-sectional views, respectively, of a protrusion according to an exemplary embodiment of the present invention;
FIG. 10A is a schematic top view of a bulk acoustic wave resonator with a prior art electrode having a void layer;
fig. 10B is a schematic cross-sectional view of the bulk acoustic wave resonator of fig. 10A taken along the line a1-a 2.
Detailed Description
The technical scheme of the invention is further specifically described by the following embodiments and the accompanying drawings. In the specification, the same or similar reference numerals denote the same or similar components. The following description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the general inventive concept of the present invention and should not be construed as limiting the invention.
The present invention is directed to an improvement of the structure of the bulk acoustic wave resonator shown in fig. 10A and 10B. Therefore, the present invention can also be applied to the description of fig. 10A and 10B.
As shown in fig. 10A and 10B, the reference numerals are as follows:
10: the substrate can be made of silicon (high-resistance silicon), gallium arsenide, sapphire, quartz, etc.
20: the acoustic mirror, shown as cavity 20, may also employ bragg reflectors and other equivalents.
30: the bottom electrode is made of molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or their composite or their alloy.
36: and the electrode pin is made of the same material as the first bottom electrode.
40: the piezoelectric thin film layer can be selected from aluminum nitride (AlN), zinc oxide (ZnO), lead zirconate titanate (PZT), and lithium niobate (LiNbO)3) Quartz (Quartz), potassium niobate (KNbO)3) Or lithium tantalate (LiTaO)3) And the rare earth element doped material with a certain atomic ratio of the materials can be contained.
50: the first top electrode is made of molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or a composite of the above metals or an alloy thereof.
56: and the electrode pin is made of the same material as the first top electrode.
60: an air gap is located within the top electrode between the first top electrode 50 and the second top electrode 70.
70: the second top electrode is made of the same material as the first top electrode 50, but the specific material is not necessarily the same as the first top electrode 50.
In the present invention, the air gap may be an air gap layer, a vacuum gap layer, or a gap layer filled with another gas medium.
In fig. 10B, a partial release hole structure 81 is defined between the non-leaded ends of the first and second top electrodes.
For a bulk acoustic wave resonator (shown in fig. 10A-10B) with an air gap in the electrodes, the air gap can effectively prevent the second top electrode or the first bottom electrode from participating in the acoustic motion of the effective area of the resonator, and at the same time, the resonator can effectively utilize the electrical advantages (reduced impedance) brought by the additional electrode.
In embodiments of the invention such as that of fig. 1, the resonator has dual-layer top electrodes 50 and 70 (i.e., a first top electrode 50 and a second top electrode 70), the top electrode 70 covering the entire upper surface of the top electrode 50 while remaining in contact with the upper surface of the top electrode 50 on the non-electrode lead side and the lead side, thereby forming an air gap 60 between the top electrodes 70 and 50.
When the resonator works, an alternating electric field is applied to the piezoelectric layer 40 through the electrodes, and as acoustoelectric energy is coupled and mutually converted, current can pass through the electrodes. Under excitation by the alternating electric field, the piezoelectric layer generates acoustic waves, and when the acoustic waves propagate upwards to the interface of the electrode layer 50 and the air gap 60 in the top electrode, the acoustic wave energy is reflected back into the piezoelectric layer 40 (because the acoustic impedance mismatch between air and electrode is very large) and does not enter the electrode layer 70. The electrode structure containing the air gap can obviously reduce the electric loss of the resonator (shown as improvement of Q value at and near the series resonance frequency) on one hand. On the other hand, the air gap acts as an acoustic barrier to the top electrode 70, thereby substantially avoiding negative effects of the electrode layer 70 on the resonator performance (e.g., changes in the resonant frequency and electromechanical coupling coefficient).
The height of the air gap is generally greater than the typical amplitude of the resonator (about 10nm), e.g., the height of the air gap is at
This facilitates the decoupling of the acoustic energy of the top electrode 70 from the resonant cavity (in this embodiment, the composite structure of the top electrode 50, the piezoelectric layer 40, and the bottom electrode 30) during high power operation of the resonator. Further, in
Within the range of (1).
In the present invention, the bottom electrode of the bulk acoustic wave resonator may be a gap electrode, and an electrode on a side close to the piezoelectric film is a first bottom electrode, and an electrode on a side far from the piezoelectric film is a second bottom electrode.
If the electrode layers on the upper and lower sides of the gap layer in the gap electrode are attached to each other and are not easily separated and reset in the working process of the resonator, the acoustic energy may leak from the contact portion to the additional electrode (the second top electrode in fig. 10B) from the effective region, and thus the second top electrode 70 is no longer acoustically isolated from the effective region, which causes parasitics in the electrical response of the resonator, and also causes the frequency of the resonator to significantly decrease due to the mass loading effect, which deteriorates the performance of the resonator, and is not favorable for the stability and improvement of the performance of the resonator.
The invention provides a technical scheme which can prevent electrode layers on the upper side and the lower side of a gap layer in a gap electrode from being attached to each other. The following examples all use the top electrode as a gapped electrode as an example, and as will be appreciated by those skilled in the art, the same embodiment can be used when the bottom electrode is also a gapped electrode.
Fig. 1 is a schematic partial cross-sectional view of a gap electrode of a bulk acoustic wave resonator according to an exemplary embodiment of the present invention, a second top electrode of the gap electrode being provided with a protrusion.
In fig. 1, 50 is a first top electrode, 70 is a second top electrode, and an air gap 60 is provided between the first top electrode 50 and the second top electrode 70, and 81 is a partial release hole structure. Wherein a plurality of minute protrusions BMP1 are provided on the lower surface of the second top electrode 70.
FIG. 2 is a schematic view of the gap electrodes of FIG. 1 attached to each other; fig. 3 is a partially enlarged view of a portion in fig. 2. As shown in fig. 2-3, if the two electrodes 50 and 70 are close to each other in a wet-out environment (as shown in fig. 3), only the top of the bump structure makes a small-area contact with the first bottom electrode 50 (as shown in the region C2 in fig. 3).
Therefore, the contact area is obviously reduced, so that the adsorption effect of the two layers of electrodes on the contact surface is greatly reduced, the two layers of electrodes can be easily separated and reset after being contacted, and the bonding phenomenon can be effectively inhibited or avoided.
Fig. 4 is a schematic partial cross-sectional view of a gap electrode of a bulk acoustic wave resonator according to an exemplary embodiment of the present invention, the first top electrode 50 of which is provided with a protrusion BMP 1.
Fig. 5 is a schematic partial cross-sectional view of a bulk acoustic wave resonator according to another exemplary embodiment of the present invention, in which the passivation layer 71 is disposed on the upper surface of the first top electrode 50, and the protrusion BMP1 is disposed directly on the passivation layer 71, which may be the same material as the passivation layer. In fig. 5, the top surface of the second top electrode 70 is also provided with a passivation layer 72.
The distribution of the protrusions is explained below with reference to fig. 6A and 6B. Fig. 6A is an exemplary diagram of a protrusion arrangement according to an exemplary embodiment of the present invention, wherein the protrusion is arranged on the second top electrode side. When the two electrode layers of the gap electrode are bonded, only a part of the electrode layers are usually in contact, and therefore, as shown in fig. 6A, the projection BMP1 may be provided only in the region where contact is most likely to occur, without extending over the entire electrode surface. The protrusions may also be distributed over the surface of the electrode side on which they are located, where the distribution may be discrete or uniform.
In a further embodiment, in the case where the electrode layers on both sides of the void layer are electrically connected to each other at both ends (non-pin end and pin end) of the void layer, for example, in a lateral direction of the resonator with reference to the drawings (which are cross-sectional views, for example, fig. 6A), the air gap may have a first end and a second end with a first distance therebetween; the protrusions may be distributed in an intermediate area between the first end and the second end in a lateral direction of the resonator. The above is described with reference to the cross-sectional views.
In practice, the protrusions are arranged in an intermediate zone, which is a circle centred on the centroid of the interstitial layer and having a radius of a first distance, which is not greater than four fifths of the shortest distance from the centroid to the edge of the interstitial layer, and further wherein the first distance is in the range of one quarter to three quarters of the shortest distance. Specifically, for example, referring to fig. 6B, it can be seen that the protrusions are distributed in the central area of the void layer of the electrode, where the central area is a circle with the centroid of the void layer as the center and R as the radius, and the shortest distance from the centroid to the edge of the void layer is d0, then R is in the range of 0.25-0.75d 0. In the present invention, the centroid is a geometric center of the void layer or a projection of a geometric center of an effective region of the resonator on the void layer.
In the case where the first electrode and the second electrode are electrically connected to each other at the lead end and are spaced apart from each other at the non-lead end in the thickness direction of the resonator, the projections are distributed closer to the non-lead end. In particular, the interstitial layer has a centroid with a shortest distance to the edge of the interstitial layer in the lateral direction of the resonator; and the protrusions are arranged in a range where a distance from the edge of the void layer is less than one-half of the shortest distance in a direction toward the centroid of the edge of the void layer. Also, in the present invention, the centroid is a geometric center of the void layer or a projection of a geometric center of an active area of the resonator on the void layer.
Fig. 7 is an exemplary schematic diagram of a protrusion distribution according to an exemplary embodiment of the present invention. In fig. 7, the protrusions are arranged in a matrix array, but other arrangements are possible. Such as a circular array distribution, a divergent distribution, etc. The spacing between the protrusions in the array may be defined. In fig. 7, the projections BMP1 may be arranged in a regular array in plan view as shown in fig. 7. The center-to-center distances between a certain projection and an adjacent projection in the transverse direction and the longitudinal direction are a and b respectively.
The shape or shape of the protrusion is explained below.
FIG. 8 is a schematic view of the profile of a protrusion according to an exemplary embodiment of the present invention; fig. 9A and 9B are a perspective view and a cross-sectional view, respectively, of a protrusion according to an exemplary embodiment of the present invention.
The specific geometry of each protrusion may be cylindrical, prismatic, conical, pyramidal, hemispherical, etc. For example, as shown in FIG. 8, the protrusions may be formed in a tapered circular truncated cone structure, wherein the height h of the protrusions may be in the range of
(or 1/10-1/2 of the thickness of the air gap) and the radius R of the bottom circular surface is in the range of0.1-20 μm, and the radius of the top circular surface is 0.05-10 μm.
The tapered shape of fig. 9A and 9B can significantly reduce the area of the contact surface at the top of the protrusion, and the curved shape of the side portion smoothly overlaps the bottom surface of the protrusion, thereby effectively preventing the protrusion from breaking. In fig. 9A and 9B, the side surfaces of the protrusions are curved surfaces that are concave toward the center line of the protrusions.
In the present invention, the top electrode is taken as an example of the gap electrode, and as can be understood by those skilled in the art, the protrusion according to the present invention may be provided in the bottom electrode as the gap electrode.
In the present invention, the numerical ranges mentioned may be, besides the end points, the median values between the end points or other values, and are within the protection scope of the present invention.
As can be appreciated by those skilled in the art, bulk acoustic wave resonators according to the present invention can be used to form filters.
Based on the above, the invention provides the following technical scheme:
1. a bulk acoustic wave resonator comprising:
a substrate;
an acoustic mirror;
a bottom electrode;
a top electrode; and
a piezoelectric layer disposed between the bottom electrode and the top electrode,
wherein:
the bottom electrode and/or the top electrode are gap electrodes, each gap electrode comprises a gap layer, a first electrode and a second electrode, the gap layers are formed between the first electrodes and the second electrodes in the thickness direction of the resonator, and the first electrodes are in surface contact with the piezoelectric layers; and is
The gap electrode includes a first surface on the first electrode side, a second surface on the second electrode side, the first surface and the second surface being opposite to each other in a thickness direction of the resonator, and a gap layer located between the first surface and the second surface;
the resonator further includes a plurality of protrusions extending from the first surface and/or the second surface into the void layer in a thickness direction of the resonator, the protrusions extending to a height less than a thickness of the void layer.
2. The resonator of claim 1, wherein:
the first surface is a surface of the first electrode, and the material of the protrusion is the same as that of the first electrode.
3. The resonator of claim 1, wherein:
the surface of the first electrode is provided with a passivation layer, the first surface is the surface of the passivation layer, and the material of the protrusion is the same as that of the passivation layer.
4. The resonator of any of claims 1-3, wherein:
the height of the protrusion is
Or
The height of the protrusions is one-half to one-tenth of the thickness of the void layer.
5. The resonator of claim 4, wherein:
the thickness of the void layer is within
Within the range of (1).
6. The resonator of claim 5, wherein:
the thickness of the void layer is within
Within the range of (1).
7. The resonator of any of claims 1-3, wherein:
the protrusions extend over the surface on which they are disposed.
8. The resonator of any of claims 1-3, wherein:
the protrusions are distributed over only a portion of the surface on which they are disposed.
9. The resonator of claim 8, wherein:
the first electrode and the second electrode are electrically connected to each other at a pin end and are electrically connected to each other at a non-pin end.
10. The resonator of claim 9, wherein:
the hollow layer is provided with a centroid, and the centroid is the geometrical center of the hollow layer or the projection of the geometrical center of the effective area of the resonator on the hollow layer;
the protrusions are arranged in a middle area which is a circle having a center at the centroid and a radius at a first distance which is not more than four fifths of a shortest distance from the centroid to an edge of the void layer, and further, the first distance is in a range of one quarter to three quarters of the shortest distance.
11. The resonator of claim 8, wherein:
the first electrode and the second electrode are electrically connected to each other at a lead end and spaced apart from each other in a thickness direction of the resonator at a non-lead end.
12. The resonator of claim 11, wherein:
the said space layer has a centroid, in the transverse direction of the resonator, the said centroid has a shortest distance to the edge of the space layer, the said centroid is the geometrical center of the said space layer or the projection of the geometrical center of the resonator's active area on the said space layer; and is
The protrusions are arranged in a range where a distance from the edge of the void layer is less than one-half of the shortest distance in a direction toward the centroid of the edge of the void layer.
13. The resonator of any of claims 1-3, wherein:
the plurality of protrusions are arranged in an array.
14. The resonator of any of claims 1-3, wherein:
the cross-sectional area of the protrusion proximate the surface thereof is greater than the cross-sectional area of the extended end of the protrusion.
15. The resonator of claim 14, wherein:
the protrusion is frustum-shaped, pyramid-shaped or hemispherical.
16. The resonator of claim 14, wherein:
the side surface of the protrusion is a curved surface which is concave towards the center line of the protrusion.
17. A filter comprising a bulk acoustic wave resonator according to any one of claims 1-16.
18. An electronic device comprising a filter according to 17 or a resonator according to any of claims 1-16.
Although embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.
Claims (19)
1. A bulk acoustic wave resonator comprising:
a substrate;
an acoustic mirror;
a bottom electrode;
a top electrode; and
a piezoelectric layer disposed between the bottom electrode and the top electrode,
wherein:
the bottom electrode and/or the top electrode are gap electrodes, each gap electrode comprises a gap layer, a first electrode and a second electrode, the gap layers are formed between the first electrodes and the second electrodes in the thickness direction of the resonator, and the first electrodes are in surface contact with the piezoelectric layers; and is
The gap electrode includes a first surface on the first electrode side, a second surface on the second electrode side, the first surface and the second surface being opposite to each other in a thickness direction of the resonator, and a gap layer located between the first surface and the second surface;
the resonator further comprises a plurality of protrusions extending from the first surface and/or the second surface into the void layer in a thickness direction of the resonator, the protrusions extending to a height less than a thickness of the void layer;
the first electrode and the second electrode are electrically connected to each other at the pin end.
2. The resonator of claim 1, wherein:
the first surface is a surface of the first electrode, and the material of the protrusion is the same as that of the first electrode.
3. The resonator of claim 1, wherein:
the surface of the first electrode is provided with a passivation layer, the first surface is the surface of the passivation layer, and the material of the protrusion is the same as that of the passivation layer.
4. The resonator of any of claims 1-3, wherein:
the height of the protrusion is 10A-2000A; or
The height of the protrusions is one-half to one-tenth of the thickness of the void layer.
5. The resonator of claim 4, wherein:
the thickness of the void layer is within a range of 50A-10000A.
6. The resonator of claim 5, wherein:
the thickness of the void layer is in a range of 100A-5000A.
7. The resonator of any of claims 1-3, wherein:
the protrusions extend over the surface on which they are disposed.
8. The resonator of any of claims 1-3, wherein:
the protrusions are distributed over only a portion of the surface on which they are disposed.
9. The resonator of claim 8, wherein:
the first electrode and the second electrode are electrically connected to each other at a pin end and are electrically connected to each other at a non-pin end.
10. The resonator of claim 9, wherein:
the hollow layer is provided with a centroid, and the centroid is the geometrical center of the hollow layer or the projection of the geometrical center of the effective area of the resonator on the hollow layer;
the protrusions are arranged in a middle area, the middle area is a circle with the centroid as a center of circle and a first distance as a radius, and the first distance is not greater than four fifths of a shortest distance from the centroid to an edge of the void layer.
11. The resonator of claim 10, wherein: the first distance is in the range of one quarter to three quarters of the shortest distance.
12. The resonator of claim 8, wherein:
the first electrode and the second electrode are electrically connected to each other at a lead end and spaced apart from each other in a thickness direction of the resonator at a non-lead end.
13. The resonator of claim 12, wherein:
the said space layer has a centroid, in the transverse direction of the resonator, the said centroid has a shortest distance to the edge of the space layer, the said centroid is the geometrical center of the said space layer or the projection of the geometrical center of the resonator's active area on the said space layer; and is
The protrusions are arranged in a range where a distance from the edge of the void layer is less than one-half of the shortest distance in a direction toward the centroid of the edge of the void layer.
14. The resonator of any of claims 1-3, wherein:
the plurality of protrusions are arranged in an array.
15. The resonator of any of claims 1-3, wherein:
the cross-sectional area of the protrusion proximate the surface thereof is greater than the cross-sectional area of the extended end of the protrusion.
16. The resonator of claim 15, wherein:
the protrusion is frustum-shaped, pyramid-shaped or hemispherical.
17. The resonator of claim 15, wherein:
the side surface of the protrusion is a curved surface which is concave towards the center line of the protrusion.
18. A filter comprising the bulk acoustic wave resonator according to any one of claims 1-17.
19. An electronic device comprising a filter according to claim 18 or a resonator according to any of claims 1-17.
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| CN107529685A (en) * | 2016-06-24 | 2018-01-02 | 三星电机株式会社 | Bulk acoustic wave resonator and the wave filter including the bulk acoustic wave resonator |
| CN109167585A (en) * | 2018-07-26 | 2019-01-08 | 开元通信技术（厦门）有限公司 | Bulk acoustic wave resonator and preparation method thereof, filter |
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| US9948272B2 (en) * | 2015-09-10 | 2018-04-17 | Qorvo Us, Inc. | Air gap in BAW top metal stack for reduced resistive and acoustic loss |
| CN107666297B (en) * | 2017-11-17 | 2024-02-09 | 杭州左蓝微电子技术有限公司 | Film bulk acoustic resonator with hydrophobic anti-adhesion structure and manufacturing method thereof |
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| CN109167585A (en) * | 2018-07-26 | 2019-01-08 | 开元通信技术（厦门）有限公司 | Bulk acoustic wave resonator and preparation method thereof, filter |
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